To add to the answer and to answer the comment (which is a bit too long to answer in a comment)
You can try thinking from the very big picture. Will reading from 2 disks be faster than 1? And the obvious answer is yes. If one disk is only capable of reading 100MBps, two disks naturally can read at 200MBps. And that's why the theoretical read speed of raid 0 is n, where n is the number of disks in the array. The same goes for raid 1 with reads. There are n number of disks and you can read from all of them at the same time for greater speed.
However, raid 0 is faster than raid 1 because there's not only reads but also writes. Raid 0 is striped, so only half the data is in one disk and the other half on the other disk. Raid 1 is cloned, so the data is on both sides. This means that when you write, you need to write to both disks of all the data in raid 1. So, the write speed in raid 0 is again n, here n is the number of disks in the array versus raid 1, where the write speed is always 1; same as writing to non-raid disk.
Also touching on the original question's misconception. You don't scan the disk to find the file's data, ever. Files have pointers which point to a block in the drive of where that file is stored in. Once you have the file in question, you fetch the data from that position and retrieve the relevant information from that block.
I suggest you read more about it in wikipedia about RAID.
Also, you can try playing around with raid calculator to see theoretical read/write speeds in wolfram alpha.